ramdisk(7D) Devices ramdisk(7D)
NAME
ramdisk - RAM disk device driver
SYNOPSIS
ramdisk@0:diskname
DESCRIPTION
The ramdisk driver supports numerous ramdisk devices that are created by the system during the boot process (see boot(1M)) or during nor-
mal system operation (see ramdiskadm(1M) for more information).
DEVICE SPECIAL FILES
Each ramdisk can be accessed either as a block device or as a raw device. When accessed as a block device, the normal buffering
mechanism is used when reading from and writing to the device, without regard to physical disk records. Accessing the ramdisk as a raw
device enables direct transmission between the disk and the read or write buffer. A single read or write call usually results in a single
I/O operation, meaning that raw I/O is more efficient when many bytes are transmitted. You can find block files names in /dev/ramdisk. Raw
file names are found in /dev/rramdisk.
There are no alignment or length restrictions on I/O requests to either block or character devices.
ERRORS
EFAULT The argument features a bad address.
EINVAL Invalid argument. EIO. An I/O error occurred.
EPERM Cannot create or delete a ramdisk without write permission on /dev/ramdiskctl.
ENOTTY The device does not support the requested ioctl function.
ENXIO The device did not exist during opening.
EBUSY Cannot exclusively open /dev/ramdiskctl. One or more ramdisks are still open.
EEXIST A ramdisk with the indicated name already exists.
EAGAIN Cannot allocate resource for ramdisk. Try again later.
FILES
/dev/ramdisk/diskname
Block device for ramdisk named diskname.
/dev/rramdisk/diskname
Raw device for ramdisk name diskname
/kernel/drv/ramdisk
32-bit driver
/kernel/drv/ramdisk.conf
Driver configuration file. (Do not alter).
/kernel/drv/sparcv9/ramdisk
64-bit driver
ATTRIBUTES
See attributes(5) for descriptions of the following attribute:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Interface Stability |Evolving |
+-----------------------------+-----------------------------+
SEE ALSO
ramdiskadm(1M), fsck(1M), fstyp(1M), mount(1M), newfs(1M), driver.conf(4), filesystem(5), dkio(7I)
NOTES
The percentage of available physical memory that can be allocated to ramdisks is constrained by the variable rd_percent_physmem. You can
tune the rd_percent_physmem variable in /etc/system. By default, the percentage of available physical memory that can be allocated to
ramdisks is fixed at 25%.
A ramdisk may not be the best possible use of system memory. Accordingly, use ramdisks only when absolutely necessary.
SunOS 5.10 04 Mar 2003 ramdisk(7D)